The present invention relates to an image forming apparatus.
In a conventional image forming apparatus such as a printer, a copier, a facsimile, a multi-function product, and the likes, a charge roller uniformly charges a surface of a photosensitive drum. An LED (Light Emitting Diode) head exposes the surface of the photosensitive drum to form a static latent image. A developing device develops the static latent image to form a toner image. A transfer roller transfers the toner image to a sheet, and a fixing device fixes the toner image to the sheet, thereby forming an image on the sheet.
The developing device is generally use toner of a one-component type. In the developing device, a tone supply roller supplies toner to a developing roller, and the developing roller attaches toner to the static latent image, thereby developing the static latent image. The toner supply roller is formed of a sponge. Accordingly, the toner supply roller tends to have a short lifetime. When a surface of the toner supply roller is deteriorated, an amount of toner supplied to the developing roller varies, thereby varying a density of an image.
To this end, instead of the developing roller, there has been proposed a developing device using a developing belt. In this case, the developing device includes a drive roller, a follower roller, and the developing belt. When the photosensitive drum rotates, the developing belt moves. It is possible to adjust a pressure between the toner supply roller and the developing belt through adjusting an extension force applied to the developing belt. Accordingly, it is possible to prolong a lifetime of the toner supply roller, and to stabilize a density of an image (refer to Patent Reference).    Patent Reference: Japanese Patent Publication No. 07-064445
In the conventional image forming apparatus described above, the toner supply roller directly abuts against the developing belt, and a voltage is applied to the toner supply roller for supplying toner to the developing belt. Accordingly, it is difficult to scrape off unused toner remaining on the developing belt with the toner supply roller. As a result, the next developing operation is performed with toner still remaining on the developing belt, thereby causing an afterimage and lowering image quality.
In view of the problems described above, an object of the present invention is to provide an image forming apparatus capable of solving the problems of the conventional image forming apparatus. In the image forming apparatus of the present invention, it is possible to prevent an afterimage from occurring and improve image quality.
Further objects of the invention will be apparent from the following description of the invention.